Various conditions that afflict the heart are treated through delivery of one or more therapeutic and/or diagnostic agents. A variety of techniques involving delivery of biological, genetic, and/or pharmacological therapeutic and/or diagnostic agents to the heart are known for treating conditions such as myocardial infarction (MI), blood clots within the coronary arteries, cardiac arrhythmias, coronary artery disease (CAD), heart failure (HF), or the like. For example, myoblasts, myocytes or stem cells may be delivered to the heart as a therapeutic and/or diagnostic agent to treat an MI (i.e., the death of muscle cells within the heart). As another example, anticoagulants such as warfarin or heparin, or enzymes such as Tissue type plasminogen activator (t-PA), Streptokinase or Urokinase are delivered to the heart to deter or dissolve blood clots within the coronary arteries.
Therapeutic and/or diagnostic agents are delivered into, for example, a chamber of the heart, blood vessels near the heart, such as the aorta, or the pericardial sac of the heart. Typically, therapeutic and/or diagnostic agents are delivered to the heart in the form of a bolus using an infusion apparatus, such as a pump or syringe, coupled to a catheter, and/or a hollow needle. However, it is generally understood that a small percentage (<10%) of a therapeutic and/or diagnostic agent delivered as a bolus actually “perfuses” (e.g., enters the coronary vasculature) of the heart, with the remaining therapeutic and/or diagnostic agent escaping to the systemic circulation.
Consequently, a bolus must include substantially more than a therapeutically effective amount of the therapeutic and/or diagnostic agent, increasing the cost of the treatment, among other disadvantages. Where an implantable drug pump is used to deliver a therapeutic and/or diagnostic agent to the heart, the requirement of excess therapeutic and/or diagnostic agent impacts the size and/or the refilling schedule of a reservoir of a drug pump. Further, the portion of the delivered therapeutic and/or diagnostic agent lost to the systemic circulation may have unintended and potentially undesirable effects on systemic and peripheral tissues of the patient to whose heart the therapeutic and/or diagnostic agent is intended to be delivered.